There are several designs for touch sensor which may be adapted for use in the presently disclosed embodiments. It is useful to examine the underlying technology of the touch sensors to better understand how any touchpad can take advantage of the presently disclosed embodiments.
The CIRQUE® Corporation touchpad is a mutual capacitance-sensing device and an example is illustrated as a block diagram in FIG. 1. In this touchpad 10, a grid of X (12) and Y (14) electrodes and a sense electrode 16 are used to define the touch-sensitive area 18 of the touchpad. Typically, the touchpad 10 is a rectangular grid of approximately 16 by 12 electrodes, or 8 by 6 electrodes when there are space constraints. Interlaced with these X (12) and Y (14) (or row and column) electrodes is a single sense electrode 16. All position measurements are made through the sense electrode 16.
The CIRQUE® Corporation touchpad 10 measures an imbalance in electrical charge on the sense line 16. When no pointing object is on, or in proximity to, the touchpad 10, the touchpad circuitry 20 is in a balanced state, and there is no charge imbalance on the sense line 16. When a pointing object creates imbalance because of capacitive coupling when the object approaches or touches a touch surface (the sensing area 18 of the touchpad 10), a change in capacitance occurs on the electrodes 12, 14. What is measured is the change in capacitance, but not the absolute capacitance value on the electrodes 12, 14. The touchpad 10 determines the change in capacitance by measuring the amount of charge that must be injected onto the sense line 16 to reestablish or regain balance of charge on the sense line.
The system above is utilized to determine the position of a finger on, or in proximity to, a touchpad 10 as follows. This example describes row electrodes 12, and is repeated in the same manner for the column electrodes 14. The values obtained from the row and column electrode measurements determine an intersection which is the centroid of the pointing object on or in proximity to the touchpad 10.
In a first step, a first set of row electrodes 12 are driven with a first signal from P, N generator 22, and a different but adjacent second set of row electrodes are driven with a second signal from the P, N generator. The touchpad circuitry 20 obtains a value from the sense line 16 using a mutual capacitance measuring device 26 that indicates which row electrode is closest to the pointing object. However, the touchpad circuitry 20 under the control of microcontroller 28 cannot yet determine on which side of the row electrode the pointing object is located, nor can the touchpad circuitry 20 determine just how far the pointing object is located away from the electrode. Thus, the system shifts by one electrode the group of electrodes 12 to be driven. In other words, the electrode on one side of the group is added, while the electrode on the opposite side of the group is no longer driven. The new group is then driven by the P, N generator 22 and a second measurement of the sense line 16 is taken.
From these two measurements, it is possible to determine on which side of the row electrode the pointing object is located, and how far away. For example, by using a routine or program that compares the magnitude of the two signals measured, and then performs pointing object position determination.
The sensitivity or resolution of the CIRQUE® Corporation touchpad is much higher than the 16 by 12 grid of row and column electrodes implies. The resolution is typically on the order of 960 counts per inch, or greater. The exact resolution is determined by the sensitivity of the components, the spacing between the electrodes 12, 14 on the same rows and columns, and other factors that are not material to the present disclosure. The process above is repeated for the Y or column electrodes 14 using a P, N generator 24
Although the CIRQUE® touchpad described above uses a grid of X and Y electrodes 12, 14 and a separate and single sense electrode 16, the sense electrode can also be the X or Y electrodes 12, 14 by using multiplexing.
Self-capacitive sensors are also known to those skilled in the art. When a sensor uses self-capacitance to measure proximity of an object to the self-capacitive sensor, it may be difficult to tell the difference between a large object at a far range and a smaller object that is at a closer range when each of these two scenarios has a similar capacitive loading on the self-capacitive sensor. For example, on a particular virtual reality controller (e.g., the VR GRIP™ by Cirque Corporation), it may be difficult to determine if a finger is extended above a sensor of the VR controller, or if a finger is actually in contact because of the various sizes of fingers that may be used. Accordingly, it would be an advantage over the state of the art in proximity controllers to provide a controller that would be able to able to determine when contact is made by a finger.
Other drawbacks, disadvantages, and issues also exist with current systems and methods.